As a massive Ronaldo fan and someone who thinks he is the GOAT, simply not. Messi is something special. What he can do, no footballer has ever been able to do in my opinion. His dribbling is a natural gift beyond what any footballer I've seen can achieve.
I can't say I've followed R9 as a teenager but Messi was 18 and was just something else.
Ask any Brazilian, this is one of the rare instances where it's not national bias, it's just that we got to watch him before the world knew he was a thing (mostly in the NT).
Messi was exciting as a teenager, Ronaldo was like an avalanche, he was widely accepted as Brazil's best player in the WC98 at just 20, but when he was 18 he was already rivaling Romario for that spot (motherfreaking Romario).
Scored 8 goals in a World Cup after what seemed a career ending injury. Remember, this is a guy who had been seldom active for 2 years!
After 2002 the injuries and early hypothyroidism issues took their toll, his shape went downhill and he stopped being so dominant.
Maybe he wouldn't have been as good as Messi, but he would not be far at all, I believe that if he had longevity, he'd be somewhere between Messi and CR7, and I think these two are definitely close between themselves. That says something.